Gas analysis apparatus



Feb. 15, 1944. KRQGH GAS ANALYSIS APPARATUS Filed May 11, 1940 2 Sheets-Sheet 1 INVENTOR.

AN ER E. KROGH AT RNEY Feb. 15, 1944. A. E. KROGH GAS ANALYSIS APPARATUS Filed May 11, 1940 2 Sheets-Sheet 2 INVENTOR.

ANKER E. KROGH ATTORNEY Patented Feb. 15. 1944 I UNITED STATES "PATENT. OFFICE 2,341,127 I GAS ANALYSIS APPARATUS Anker E. Krog-h, Philadelphia, I'a., assignor to The Brown Instrument Company, Philadelphia,

Pa., a corporation of Pennsylvania Application May 11, 1940, Serial No. 334,677

I (Cl. 7-3-51) I 2 Claims.

The present invention relates to control instruments and more particularly to a system for analyzing the gases in a furnace and controlling the fuel to the furnace in response to the analysis of the gas.

' In various types of furnaces it is desirable to keep, either'an oxidizing or a reducing atmosphere depending upon the use to which the furnace is put. In ordinary boiler furnaces it has been found that for maximum efficiency it is necessary to keep the CO2 content of the exhaust gases at some predetermined percentage. In

either case various instruments that have been developed for analyzing gases are used to analyze the furnace or exhaust gases and to control the ingredient which-affects the analysis. Systems of this type often have an objectionable lag between, the time a sample of thegas in question is taken and the time-that the result of the analysis is reflected in an operation of the control device- This lag is often due to the slowing down of the sample of gases itflows through'a series of filters between the point at which the sample was taken and the point at which an analysis is made of the gas.

It is an object of the present invention to pro vide a means for rapidly and efliciently'cleaning a sample of gas to be analyzedwithout ii'ecting the flow ofthe gas. It is a further the invention to remove dirt and moisture from a continuously flowing sample ofgas without subjecting the gas to any retarding influence.

biect of it is a further object of the invention to pass a sample of gas going from a point of origin to a point of analysis through a cooling or refriggas sample is reduced, the gas, before it enters the analyzing space, may be made to have any desired relative humidity. This feature is of ime portance since each of various types of analyzing apparatus function best when the gas to be analyzed is at some particular relative humidity.

Thus a clean gas of the proper humidity is in ,troduced to the analyzing space.

.placed, or for any use in which it is desired to cleanagas.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming apart of this specification. For a better under-- standing of the invention, however, its-advantages and specific objects obtained with its use,.

reference should be'had to the accompanying drawings and descriptive matter in whichI have illustrated and described a preferred embodiment of the invention.

In the drawings:

Fig. 1 shows a system for analyzing a gas and controlling the analysis thereof; Fig. 1A is a view of the temperature controller;

Fig. 2 is a sectional View showing the inside of the refrigerator tank used in this system; and

Fig. 3 is a diagrammatic wiring diagram of a thermal conductivity measuring system- Referring. to Figure 1, there is shown a furnace l whose atmosphere is to be measured, the furnace being supplied with fuel through a burner 2 that is in turn supplied with air through pipe 8 and fuel through pipe 4. When the atmosphere of the furnace varies from the predetermined may be of the air-controlled potentiometer type shown in Harrison Patent 2,112,091. This instrument is supplied with air under pressure through a line 8 and in response to measurements made of the furnace atmosphere varies ,the pressure While the apparatus is described herein as. being used to analyze and controlafurnace atmosphere, the invention is applicable for any appliedthrough line 6 to the valve 5.

. c A sample ofthefumace atmosphere is taken. through a water cooled'outlet 8 that is supplied with cooling liquid through the pipe ID. The

sample of gas is drawn from outlet 9' through a pipe ii to arefrigerator tank' H which serves to cool the gas and precipitate out moisture and dirt and the gas is then passed through a thermail-conductivity analyzing cell it.

The refrigerating unit indicated generally at it consists of a heavily insulated tank it which formed with a suitable liquid such as calciumchloride brine. Within the tank is arefrigerating coil Iii that is supplied with refrigerant through an" expansion valve HAthat is located use ta which an analyzing apparatus'may best in theiplet pipe I! to the coil It. This pipe is means of the temperature controller 13 connected by capillary 20 to a temperature responsive bulb 2| that is located in the brine. The controller l9 may be of the type shown and described in Cunningham Patent 2,014,050, or in Shipley Patent 2,080,836 but is shown diagrammatically herein in Figure 1A as comprising a bellows 60 connected to the end of capillary which bellows expands and contracts as the temperature of the bulb 2| changes. The movement of the bellows 60 serves to tilt a support 6! for a mercury switch 62 around its pivot to open or close the switch. The bellows acts against the force of a spring 63 whose force may be adjusted by means of a nut 34 acting on a screw threaded member 65 attached to the lower end of the spring. Changing the force of the spring serves to change the control point of the instrument or the temperature it will tend to maintain. As the temperature of the brine rises above some predetermined value the temperature controller I9 serves to close the switch 62 to complete a circuit between lines 22 and 23 to'energize compressor unit E6 to lower the temperature of the tank.

A sample of air from the line I l passes into the tank 54 through a pipe 24 that is connected by a short pipe 25 with an exit pipe 26. The pipes 2s and 26 along with a third pipe 21 serve as legs to support the tank I4 by means of a base 28. The legs comprising pipes 24, 26 and 21 are held together by means of a hollow sealing member 29 which has a drain pipe 30 extending from it. After leaving the tank [4 through the pipe 28, the sample of gas passes through pipe 3| and a secondary filter 92, which may or may not be necessary, to the cell I3 and f om there is exhausted through pipe 33. A constantly running motor driven pump 34 is used to continuously draw a sample of the air from the furnace through the refrigerating unit and the analyzing cell to exhaust it either to the atmosphere or back into the furnace as the case may be. The pump drive motor is. preferably of. the variable speed type so that its speed may be varied in to keep a constant but easily adjusted flow of gas through the sampling line. The amount of this flow is visually shown by means of a draft gauge 3? that is located in pipe 33 on the exhaust side of the cell i3. A by-pass line 38 is provided around the cell i3 so that the cell may be disconnected if necessary. The cell is connected to the instrument i through suitable wiring 39 and 40. Suitable valves are provided along the sampling line so that various of the units may be disconnected if desired. For example, a valve 4! is provided in the pipe 24 to shut ed the supply of gas from pipe ll. Valves 42 and 43 are provided in lines 3i and 33 so that the flow of gas may be shut off through the cell [3 and the cell removed from the system. A drain valve 4 as is provided in the line just in front of the cell 93 so that the system can be "rained or blown out if necessary, and a valve 45, in the by-pass any desired type depending upon the gas that is concentra ion measuring system that may be of to be kept-atsome predetermined value within the furnace. The system can be used to either maintain an oxidizing or a reducing atmosphere in the furnace l but it may also be used tomaintain a predetermined carbon dioxide content of the exhaust gases of a furnace.

'The'gas concentration measuring device I! con- I former of which is sealed as shown and contains a sample of the gas the concentration of which it is desired to measure, or a sample of any suitable comparison gas in accordance with the wellknown conductivity principle of gas analysis. This compartment 46 also contains a resistance wire 48 which has a substantial temperature coeilicient and forms one arm of a Wheatstone bridge. The other compartment 41 of the measuring device is fed by the tube 3| with the sample of gas to be tested and is connected with the exhausttube 33. Because of its connections with the furnace I, a continuous sample of gas therefrom may pass through the chamber 41 and over a resistance wire 49 therein which also has a substantial temperature coefllcient and forms another arm of the Wheatstone bridge. The resistances 50 and 5| form the other arms of the Wheatstone bridge and are connected at their respective ends by a resistance 52 with which is associated a contact 53.

A galvanometer 54 is inserted in the bridge circuit to detect any unbalance thereof as the quality of the gas flow through chamber 41. varies.

The measuring device could, of course, be of the deflectional type in which the deflections of the pointer constitute a measure of the gas composition but, preferably this instrument is of the automatic self-balancing, or null type, in which the contact 53 is continuously moved to a position in which the bridge circuit is balanced and a pointer 55, associated therewith, may indicate on a scale 56 the vahie of the gas concentration. While the adjustment of valve' 5 could be manually changed in accordance with the deflections of the galvanometer in the deflectional typ and of the pointer 5 in the null type, it is preferred to adjust the valve automatically. Accordingly, the galvanometer 54 is herein shown designed to form part of a suitable relay or control mechanism designated generally by the reference numeral 1 and is shown as being of the type decell l3 passing, on its way, through the refrig crating unit l2. This unit serves to cool down the gas and in so doing increases its relative humidity to a point where excess moisture will precipitate from the gas and drop'down through pipes 24 and 26 to the sealing unit 29 where it will be discharged through the exhaust pipe 36. As the moisture precipitates out of the gas sample it will carry along with it any dirt or dust that may be in the sample, thus permitting only clean gas to go to the cell l3. As the gas passes from the pipe 26 through pipe 3| to the cell l3 it is outside of the refrigerated zone and will be warmed suihciently so that its relative humidity is decreased to a point where the conducmoisture in thegas sample can be'removed and l,

the amount of heating of the gas that is accomplished as it passes through the pipe 3| can be varied. Therefore, gas of any desired relative humidity may be had inthe cell l3 so that this cell will work with the maximum efllciency. The filter 32 may. or may not be necessary depending upon the type of gas that is being measured, but in any event, the large amount of dirt and moisture that is removed from the gas sample by means of the refrigerating process will leave the gas so clean that the efl'ect of the filter 32 onthe flow of the sample is negligible and it will last indefinitely without having the fllter material changed. Thus it is seen that a continuous sample of gas is drawn upwardly from the furnace to the measuring instrument and that' the analysis of this sample is quickly made so that the control valve 5 will be operated practi-- cally as soon as the gassample has been drawn from the furnace. This short period between the time a sample is taken and the time a control impulse is given to the valve 5 means that a more accurate control is obtained than has heretofore been obtained by a system in which there was a lag between the time that the sample was withdrawn from the furnace and the time. that a control impulse was given to the valve as a result.

of the measurement of that sample.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that in some cases certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

Having now described-my invention, what I claim as new and desire to secure by Letters Patentis:

1. In a measuring system, means to create a continuous sample flow of gas to be analyzed and means to clean said gas without resistance to its flow comprising a pair of vertically ex'- tending in-flow and out-flow pipes through which said gas flows, a fluid connection between said pipes, the lower end of said pipes bein'g immersed in a sealingliquid and means surrounding said pipes to cool the gas flowing therethrough to a predetermined degree which is below its dew point, said connection being adjacent the lower end of said surrounding means, said surrounding means comprising a tank and a refrigerating coil in said tank, and means to adjust the temperature of said refrigerating coil to vary the moisture precipitated and therefore the relative humidity of the gas.

2. In a gas analyzing system, means to create a continuous sample flow of gas to be analyzed and means to clean and remove moisture from said gas comprising a pair of vertically extending inflow and outflow pipes through which said gas flows. cooling means surrounding said pipes to cool the gas'fiowing therethrough to a predetermined degree which is below its dew point, a trap,

receiving the lower ends of said pipes for removing condensate from the pipes, a fluid connection between the pipes'near the lower ends thereof, and means to adjust the temperature of said cooling means to vary the moisture precipitated and therefore the relative humidity of the gas.

ANKER. E. KROGH. 

